1. Field of the Invention
The present invention relates to a non-reducible low temperature sinterable dielectric ceramic composition for a multilayer ceramic capacitor (MLCC) and a manufacturing method thereof, and more particularly, to a non-reducible low temperature sinterable dielectric ceramic composition for an MLCC that may mix a main component and an auxiliary main component having a phase different from the main component, thereby preventing a degradation in reliability that occurs due to a decrease in dielectric thickness according to high capacitance, and a manufacturing method thereof.
2. Description of the Related Art
A multilayer ceramic capacitor (MLCC) is manufactured by molding a dielectric sheet using a dielectric ceramic composition, disposing the dielectric sheet and an internal electrode, and sintering the same in an atmospheric atmosphere. BaTiO3 powder is used as a main material of the dielectric ceramic composition for manufacturing the MLCC.
The BaTiO3 powder is ferroelectrics having a perovskite phase constitution, and is being used as a main material of a non-reducible dielectric ceramic composition of the MLCC due to a high dielectric constant, thermal stability, and low price. A method of manufacturing such BaTiO3 powder includes a hydrothermal method, a solid state reaction method, and the like.
Compared to other manufacturing methods, the hydrothermal method is excellent in manufacturing uniform and ultrafine particles and does not require additional heat treatment and milling processing. However, compared to the solid state reaction method, manufacturing cost is high, a reaction time is long, and it is difficult to adjust a concentration of titanium oxide hydrate. The solid state reaction method is a commercially widely used method, and manufactures BaTiO3 powder by employing, as starting materials, BaCO3 and TiO2, and by performing diffusion control reaction in about 900 to 1400° C. The solid state reaction method has an advantage in that manufacturing cost is low, but has a disadvantage in that a minimum size of manufactured powder is about 0.5 μm and particle distribution is uneven.
Korean Registered Patent No. 327132 (Registered Date: 2002.02.21) relates to a dielectric ceramic composition and an electronic product using BaTiO3 manufactured using the aforementioned method. The dielectric ceramic composition disclosed in Korean Registered Patent No. 327132 is composed using a main component BaTiO3, and Cr2O3: 0.1 to 3 mol, V2O5: 0.01 to 0.5 mol, rare earth oxide (R1:Y, Ho, Dy): 0.7 to 7 mol, and MnO: 0.5 mall or less with respect to the main component 100 mol. Rare earth oxide constituting the conventional dielectric ceramic composition prevents the main component BaTiO3 from being degraded due to electron migration that occurs due to an electric field and an ion poor phenomenon. Accordingly, a temperature characteristic or a change in capacitance is small in a direct current (DC) electric field. By increasing a lifespan of insulation resistance, it is possible to enhance long-term reliability of the MLCC.
In the case of manufacturing the conventional dielectric ceramic composition, price of rare earth oxide added as an addition agent for the long-term reliability of the MLCC is currently increasing. Accordingly, manufacturing cost of non-reducible low-temperature sinterable dielectric ceramic composition is also increasing.